This application claims the priority of Korean Patent Application No. 2003-37138, filed on Jun. 10, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a video processing method and a video processing apparatus, and more particularly, to a method and an apparatus for performing an inverse telecine process by identifying telecine images composed of fields from different frames by calculating for each frame the total absolute local (within a given block) difference between the luminance of pixels of each field (within the block), as a field-correlation indicator. Also, the present invention relates to a computer-readable recording medium, which stores a computer program for performing the inverse telecine method.
2. Description of the Related Art
FIG. 1 is a view for describing a telecine process and an inverse telecine process. Inverse telecine (“IVTC” or “3:2 Pulldown”) is applicable to cinematic film content that was transferred to NTSC video. Because film is filmed at 24 frames per second (fps) and the NTSC standard is 30 fps, a “telecine” process must be used to add (duplicate) certain frames when the film content is transferred to video. When the content is converted back from 30 fps to 24 fps (e.g., when video content is encoded using digital technology), an inverse telecine process is used to remove these duplicate frames, thus saving file size.
Movies, advertisements, or TV soap operas (hereinafter referred to collectively as movies) filmed using a movie camera are produced at 24 fps (frames per second). To be displayed by a National Television System Committee (NTSC) broadcasting system, the movies must be converted into 30 fps rate form. The conversion is made by adding (interlacing) duplicated fields to a selected one of the original fields of a frame (image) to produce telecine images. A telecine machine does something called pulldown, which, in its simplest explanation, “pulls down” an extra frame every fourth frame to make five whole frames instead of four. Every four frames are converted into five frames by adding two additional (interlaced) fields. This process is referred to as a telecine process or a 3:2 pull-down process.
While NTSC has a frame rate of 29.97, the screen is actually being partially redrawn every 59.94 times a second. A half-frame is being drawn to the screen every 60th of a second, in other words. This leads to the notion of fields. The “Top” field of a frame includes all of the pixels in the “odd” horizontal lines of the frame, including the top horizontal line. The “Bottom” field of a frame includes all of the pixels in the “even” horizontal lines of the frame, including the top bottom line. Each full scan of even numbered lines, or odd numbered lines constitutes a “field”. Thus, each field contains half of the image data of one frame, and two fields (top and bottom fields) are interlaced to form one frame.
Telecined 30 fps frames are usually 3 progressive frames followed with 2 interlaced frames. The first frame of film is represented by 2 fields of video; the second frame of film is represented by 3 fields of video (1.5 frames); the third frame of film is again represented by two fields and the fourth frame of film is represented by 3 fields, and so on.
Referring to FIG. 1, FF1 through FF4 represent film frames, 1T, 1B, 1T(r), 2B, 2T, 3B, 3T, 3B(r), 4T, and 4B represent fields formed (extracted from frames) by the 3:2 pull-down processes, and BF1 through BF5 represent video frames formed through a telecine process (also called a “3:2 pull-down” process).
Here, generally, iT (where “i” is natural number) denotes the top field of an i-th frame, iB is the bottom field of the i-th frame, iT(r) is a duplicate of the top field of the i-th frame, and iB(r) is a duplicate of the bottom field of the i-th frame.
FIG. 2 is a simple block diagram illustrating the basic input and output of an apparatus 200 for implementing an inverse telecine process. Referring to FIGS. 1 and 2, the inverse telecine (or de-interlacing) is a process for reconverting a video frame (VF) at 30 fps (exactly, 29.976 fps) back into a film frame (FF) at 24 fps (exactly 23.976 fps).
The inverse telecine process is for recovering the original film frame (FF) by exactly identifying the video frame (VF, hereinafter referred to as telecine image) formed by a 3:2 pull-down process.
The most critical operation in the inverse telecine (or de-interlacing) process is identifying (recognizing) the 3:2 pull-down process (sequence). In a case where the 3:2 pull-down process (sequence) is changed by noise or by a changed scene, the film frames (FF) recovered may not be recovered exactly the same as the original film frames.